I have read your opinion on the tonal quality of ceramic, alnico and field-coil drivers, but what do you think of neodymium magnets? Are they much the same as ceramic? Thanks.

The British author John Watkinson has written on this subject in a series of articles called "Speakers Corner" appearing in Electronics World several years ago. I would have the article, but not to hand. His theory is that ferrites, being insulators, allow the magnetic domains to move about when subjected to forces of attraction/repulsion as work is being done moving the cone. He further suggests that this movement is not benign but rather granular/quantum. The end result is that the sounds produced are accompanied by noise sidebands, leading to the conclusion that if you are listening to a CD on a ferrite magnet speaker you are effectively not hearing what 16 bit resolution is capable of! He did concede that ferrite magnets do have uses including holding messages on the 'fridge door and picking up the metal turnings from the lathe when making experimental pole pieces.

Of course the other thing that characterises ferrites is the unpredictability of their magnetic properties. I remember being attracted to ferrite cored tape heads in the 1970's mainly in relation to their hardness and long life. A conversation with someone more knowledgable on the subject soon convinced me that the hardness was the only thing they had going for them. It was difficult to control the gap width and the inductances of a multitrck head could vary from 150 mH to 600 mH.

The end result is that the sounds produced are accompanied by noise sidebands, leading to the conclusion that if you are listening to a CD on a ferrite magnet speaker you are effectively not hearing what 16 bit resolution is capable of! He did concede that ferrite magnets do have uses including holding messages on the 'fridge door and picking up the metal turnings from the lathe when making experimental pole pieces.

His theory is that ferrites, being insulators, allow the magnetic domains to move about when subjected to forces of attraction/repulsion as work is being done moving the cone. He further suggests that this movement is not benign but rather granular/quantum. The end result is that the sounds produced are accompanied by noise sidebands, leading to the conclusion that if you are listening to a CD on a ferrite magnet speaker you are effectively not hearing what 16 bit resolution is capable of!

In any magnetic material, whenever magnetic domains change orientation, there is always hystersis, and they reorient in unsmooth jumps and cascades. The degree to which the magnetic materiel is electrically conductive will allow the formation of partially shielding/cancelling eddy currents. However, eddy-current formation is a phenomenon that increases with frequency, so they offer little help in the mid/bass. Here's a simulation of what I am talking about, using the example of copper shorting rings.

IMO, it's useful to think of a magnetic motor as a transformer. Like a transformer, it should be designed to operate over a certain bandwidth and within a certain power range, so that its operating point on the BH curve is in the most linear range. And the more power it has to handle, the less ideally it will behave. This is one reason why high-efficiency drivers can sound so good--there's less voice-coil flux pushing the magnetic material around to create a given SPL.

JBL engineers compensated for poorer flux-modulation performance of ferrite vs. AlNiCo by adding back in a path for eddy currents to flow--a shorting ring--that AlNiCo magnets provided natively with their higher conductivity. The net result works very well (except at lower frequencies, as I mentioned, where AlNiCo wouldn't fare much better in terms of flux modulation).

The British author John Watkinson has written on this subject in a series of articles called "Speakers Corner" appearing in Electronics World several years ago.*** His theory is that ferrites, being insulators, allow the magnetic domains to move about when subjected to forces of attraction/repulsion as work is being done moving the cone. ***

A "theory" ("conjecture" is a more appropriate term) is nice and all.

But without measurement data and listening tests, who cares? Without data, it's just someone spouting off.

I've enjoyed the ME2 version for quite awhile now, (bi-amped). Several years ago I started noticing some "leanness?" in the mid-bass. I ran a sweep, sure enough a drop-off/hole in the FR at 95-100 hz. I ran each P13 and thought they were mislabled MH's!! FS has risen to 102 hz to 112 hz on the four. I would guess this is caused by the surrounds aging, (brush a finger across the surrounds and they feel like an old pencil eraser). Seems like any "treatment" would cause it to completely degrade. Any ideas?
For now I moved the x-over point to 150 hz.

To clarify the above (edit apparently turned off), my ME2's are run with the mk6 crossover and tube amplification, electroncally crossed over at lower frequencies (was 80hz, now 150hz) to SS amp and woofer modules.